Apparatus for measuring or determining the surface shape of an object finds applications in many areas. In some instances, the measuring device can be physically traversed across the surface of the object, whereby instruments record and store the shape of the path traversed.
In other situations, it is highly desirable to determine the surface shape of the object without making physical contact with the object. The measurement of the shape of the cornea of an eye is one such situation. Here, it would be extremely difficult, if not impossible, to determine the angle of curvature of the cornea by passing the measuring device physically across the surface of the cornea.
The advent of contact lenses which are worn directly on the cornea of the eye dictates that the examining doctor ascertain the exterior surface shape of the cornea very accurately. Accordingly, techniques for measuring corneal shapes are described or referred to in U.S. Pat. Nos. 3,895,860 and 3,972,602. Ophthalmometers or Keratometers are thus well known in the art for making corneal measurements.
While such instruments accomplish the desired result, they are complicated to manufacture as well as to operate, and moreover, the precision with which a measurement can be made is a function of the examiner's skill. The noted ophthalmometers and Keratometers typically rely on the use of focused light beams, together with multiple prisms and lenses, to project measurement images on the cornea.
U.S. Pat. No. 4,157,859 describes a microscope system for projecting an image on the cornea and for optically splitting the image. Disclosed in U.S. Pat. No. 4,019,813 is the use of a series of lenses and a light source, together with television and video equipment for processing the information. In yet another U.S. Pat. No. 3,895,860, there is disclosed a method of making corneal measurements using the photographic record made by a keratoscope, and from such record creating a parameter which can be used for comparing subsequent corneal measurements.
From the foregoing, it can be seen that there is a need for apparatus which is not unduly complicated to manufacture, or use, and which does not depend upon subjective judgments of the eye examiner.
Even more importantly, there is a need for a method of determining the shapes or curvatures without taking special precautions as to the surrounding ambient light, and which methods can be easily adapted for many other applications.